This invention relates to an engine igniter for an internal combustion engine. More particularly, it relates to an engine igniter which can control the advance and lag angle characteristics of an engine over a wide range and which can prevent the reverse rotation of the engine.
An internal combustion engine is equipped with an engine igniter which controls the ignition timing of the engine in accordance with the engine speed, the ignition advance or lag angle being increased or decreased as the engine speed increases or decreases. A conventional engine igniter includes a signal coil mounted on a generator of the engine. As the generator is driven to rotate by the engine during its operation, the signal coil generates in succession two reference signals within a single half cycle of the output of the generator. One of these reference signals is an advance-side reference signal which is used to determine an appropriate advance angle and a lag angle for ignition timing control during the forward rotation of the engine, while the other is a lag-side reference signal which is used to prevent reverse rotation of the engine. More specifically, an ignition control unit calculates an appropriate ignition timing or crankshaft angle based on the advance-side reference signal and produces an ignition control signal which controls an ignition coil so that a spark plug of the engine is fired at an appropriate crankshaft angle. The advance angle for high-speed engine rotation and the lag angle for low-speed engine rotation are both calculated from the advance-side reference signal, and hence the lag ignition timing is farther away from the advance-side reference signal than the advance ignition timing.
With the conventional generator as described above, since both of the advance angle and the lag angle are calculated from the advance-side reference signal, there arises the following problem. Specifically, if the difference between the advance ignition timing and the lag ignition timing is to be set to a rather great value, the lag ignition timing will be accordingly far behind from the time of generation of the advance-side reference signal, at which various factors including the engine speed for ignition control are measured or detected, resulting in a tendency of fine and accurate ignition control becoming difficult. To avoid this problem, the above difference is required to be rather small, and therefore the ignition timing can be varied over only a narrow range.